diff --git a/src/evalfunc.c b/src/evalfunc.c
index f8af8ef..21d28af 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -403,12 +403,16 @@
  * Lists of functions that check the argument types of a builtin function.
  */
 argcheck_T arg1_string[] = {arg_string};
-argcheck_T arg3_string_nr_bool[] = {arg_string, arg_number, arg_bool};
+argcheck_T arg1_number[] = {arg_number};
 argcheck_T arg1_float_or_nr[] = {arg_float_or_nr};
+argcheck_T arg2_float_or_nr[] = {arg_float_or_nr, arg_float_or_nr};
+argcheck_T arg2_number[] = {arg_number, arg_number};
 argcheck_T arg2_listblob_item[] = {arg_list_or_blob, arg_item_of_prev};
 argcheck_T arg2_execute[] = {arg_string_or_list, arg_string};
 argcheck_T arg23_extend[] = {arg_list_or_dict, arg_same_as_prev, arg_extend3};
 argcheck_T arg23_extendnew[] = {arg_list_or_dict, arg_same_struct_as_prev, arg_extend3};
+argcheck_T arg3_string[] = {arg_string, arg_string, arg_string};
+argcheck_T arg3_string_nr_bool[] = {arg_string, arg_number, arg_bool};
 argcheck_T arg3_insert[] = {arg_list_or_blob, arg_item_of_prev, arg_number};
 
 /*
@@ -670,25 +674,25 @@
 {
     {"abs",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_any,	    FLOAT_FUNC(f_abs)},
-    {"acos",		1, 1, FEARG_1,	    NULL,
+    {"acos",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_acos)},
     {"add",		2, 2, FEARG_1,	    NULL /* arg2_listblob_item */,
 			ret_first_arg,	    f_add},
-    {"and",		2, 2, FEARG_1,	    NULL,
+    {"and",		2, 2, FEARG_1,	    arg2_number,
 			ret_number,	    f_and},
     {"append",		2, 2, FEARG_2,	    NULL,
 			ret_number_bool,    f_append},
     {"appendbufline",	3, 3, FEARG_3,	    NULL,
 			ret_number_bool,    f_appendbufline},
-    {"argc",		0, 1, 0,	    NULL,
+    {"argc",		0, 1, 0,	    arg1_number,
 			ret_number,	    f_argc},
     {"argidx",		0, 0, 0,	    NULL,
 			ret_number,	    f_argidx},
-    {"arglistid",	0, 2, 0,	    NULL,
+    {"arglistid",	0, 2, 0,	    arg2_number,
 			ret_number,	    f_arglistid},
-    {"argv",		0, 2, 0,	    NULL,
+    {"argv",		0, 2, 0,	    arg2_number,
 			ret_argv,	    f_argv},
-    {"asin",		1, 1, FEARG_1,	    NULL,
+    {"asin",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_asin)},
     {"assert_beeps",	1, 2, FEARG_1,	    NULL,
 			ret_number_bool,    f_assert_beeps},
@@ -716,9 +720,9 @@
 			ret_number_bool,    f_assert_report},
     {"assert_true",	1, 2, FEARG_1,	    NULL,
 			ret_number_bool,    f_assert_true},
-    {"atan",		1, 1, FEARG_1,	    NULL,
+    {"atan",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_atan)},
-    {"atan2",		2, 2, FEARG_1,	    NULL,
+    {"atan2",		2, 2, FEARG_1,	    arg2_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_atan2)},
     {"balloon_gettext",	0, 0, 0,	    NULL,
 			ret_string,
@@ -780,7 +784,7 @@
 			ret_number,	    f_byteidxcomp},
     {"call",		2, 3, FEARG_1,	    NULL,
 			ret_any,	    f_call},
-    {"ceil",		1, 1, FEARG_1,	    NULL,
+    {"ceil",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_ceil)},
     {"ch_canread",	1, 1, FEARG_1,	    NULL,
 			ret_number_bool,    JOB_FUNC(f_ch_canread)},
@@ -832,7 +836,7 @@
 			ret_string,	    f_chdir},
     {"cindent",		1, 1, FEARG_1,	    NULL,
 			ret_number,	    f_cindent},
-    {"clearmatches",	0, 1, FEARG_1,	    NULL,
+    {"clearmatches",	0, 1, FEARG_1,	    arg1_number,
 			ret_void,	    f_clearmatches},
     {"col",		1, 1, FEARG_1,	    NULL,
 			ret_number,	    f_col},
@@ -848,9 +852,9 @@
 			ret_number,	    f_confirm},
     {"copy",		1, 1, FEARG_1,	    NULL,
 			ret_first_arg,	    f_copy},
-    {"cos",		1, 1, FEARG_1,	    NULL,
+    {"cos",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_cos)},
-    {"cosh",		1, 1, FEARG_1,	    NULL,
+    {"cosh",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_cosh)},
     {"count",		2, 4, FEARG_1,	    NULL,
 			ret_number,	    f_count},
@@ -858,7 +862,7 @@
 			ret_number,	    f_cscope_connection},
     {"cursor",		1, 3, FEARG_1,	    NULL,
 			ret_number,	    f_cursor},
-    {"debugbreak",	1, 1, FEARG_1,	    NULL,
+    {"debugbreak",	1, 1, FEARG_1,	    arg1_number,
 			ret_number,
 #ifdef MSWIN
 	    f_debugbreak
@@ -898,7 +902,7 @@
 			ret_string,	    f_exepath},
     {"exists",		1, 1, FEARG_1,	    NULL,
 			ret_number_bool,    f_exists},
-    {"exp",		1, 1, FEARG_1,	    NULL,
+    {"exp",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_exp)},
     {"expand",		1, 3, FEARG_1,	    NULL,
 			ret_any,	    f_expand},
@@ -926,11 +930,11 @@
 			ret_list_any,	    f_flatten},
     {"flattennew",	1, 2, FEARG_1,	    NULL,
 			ret_list_any,	    f_flattennew},
-    {"float2nr",	1, 1, FEARG_1,	    NULL,
+    {"float2nr",	1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_number,	    FLOAT_FUNC(f_float2nr)},
-    {"floor",		1, 1, FEARG_1,	    NULL,
+    {"floor",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_floor)},
-    {"fmod",		2, 2, FEARG_1,	    NULL,
+    {"fmod",		2, 2, FEARG_1,	    arg2_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_fmod)},
     {"fnameescape",	1, 1, FEARG_1,	    NULL,
 			ret_string,	    f_fnameescape},
@@ -986,11 +990,11 @@
 			ret_string,	    f_getcmdwintype},
     {"getcompletion",	2, 3, FEARG_1,	    NULL,
 			ret_list_string,    f_getcompletion},
-    {"getcurpos",	0, 1, FEARG_1,	    NULL,
+    {"getcurpos",	0, 1, FEARG_1,	    arg1_number,
 			ret_list_number,    f_getcurpos},
-    {"getcursorcharpos",	0, 1, FEARG_1,	    NULL,
+    {"getcursorcharpos",	0, 1, FEARG_1,	    arg1_number,
 			ret_list_number,    f_getcursorcharpos},
-    {"getcwd",		0, 2, FEARG_1,	    NULL,
+    {"getcwd",		0, 2, FEARG_1,	    arg2_number,
 			ret_string,	    f_getcwd},
     {"getenv",		1, 1, FEARG_1,	    NULL,
 			ret_any,	    f_getenv},
@@ -1006,7 +1010,7 @@
 			ret_string,	    f_getftype},
     {"getimstatus",	0, 0, 0,	    NULL,
 			ret_number_bool,    f_getimstatus},
-    {"getjumplist",	0, 2, FEARG_1,	    NULL,
+    {"getjumplist",	0, 2, FEARG_1,	    arg2_number,
 			ret_list_any,	    f_getjumplist},
     {"getline",		1, 2, FEARG_1,	    NULL,
 			ret_f_getline,	    f_getline},
@@ -1014,7 +1018,7 @@
 			ret_list_or_dict_1, f_getloclist},
     {"getmarklist",	0, 1, FEARG_1,	    NULL,
 			ret_list_dict_any,  f_getmarklist},
-    {"getmatches",	0, 1, 0,	    NULL,
+    {"getmatches",	0, 1, 0,	    arg1_number,
 			ret_list_dict_any,  f_getmatches},
     {"getmousepos",	0, 0, 0,	    NULL,
 			ret_dict_number,    f_getmousepos},
@@ -1030,19 +1034,19 @@
 			ret_dict_any,	    f_getreginfo},
     {"getregtype",	0, 1, FEARG_1,	    NULL,
 			ret_string,	    f_getregtype},
-    {"gettabinfo",	0, 1, FEARG_1,	    NULL,
+    {"gettabinfo",	0, 1, FEARG_1,	    arg1_number,
 			ret_list_dict_any,  f_gettabinfo},
     {"gettabvar",	2, 3, FEARG_1,	    NULL,
 			ret_any,	    f_gettabvar},
     {"gettabwinvar",	3, 4, FEARG_1,	    NULL,
 			ret_any,	    f_gettabwinvar},
-    {"gettagstack",	0, 1, FEARG_1,	    NULL,
+    {"gettagstack",	0, 1, FEARG_1,	    arg1_number,
 			ret_dict_any,	    f_gettagstack},
     {"gettext",		1, 1, FEARG_1,	    NULL,
 			ret_string,	    f_gettext},
-    {"getwininfo",	0, 1, FEARG_1,	    NULL,
+    {"getwininfo",	0, 1, FEARG_1,	    arg1_number,
 			ret_list_dict_any,  f_getwininfo},
-    {"getwinpos",	0, 1, FEARG_1,	    NULL,
+    {"getwinpos",	0, 1, FEARG_1,	    arg1_number,
 			ret_list_number,    f_getwinpos},
     {"getwinposx",	0, 0, 0,	    NULL,
 			ret_number,	    f_getwinposx},
@@ -1060,7 +1064,7 @@
 			ret_number_bool,    f_has},
     {"has_key",		2, 2, FEARG_1,	    NULL,
 			ret_number_bool,    f_has_key},
-    {"haslocaldir",	0, 2, FEARG_1,	    NULL,
+    {"haslocaldir",	0, 2, FEARG_1,	    arg2_number,
 			ret_number,	    f_haslocaldir},
     {"hasmapto",	1, 3, FEARG_1,	    NULL,
 			ret_number_bool,    f_hasmapto},
@@ -1104,15 +1108,15 @@
 			ret_first_arg,	    f_insert},
     {"interrupt",	0, 0, 0,	    NULL,
 			ret_void,	    f_interrupt},
-    {"invert",		1, 1, FEARG_1,	    NULL,
+    {"invert",		1, 1, FEARG_1,	    arg1_number,
 			ret_number,	    f_invert},
     {"isdirectory",	1, 1, FEARG_1,	    NULL,
 			ret_number_bool,    f_isdirectory},
-    {"isinf",		1, 1, FEARG_1,	    NULL,
+    {"isinf",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_number,	    MATH_FUNC(f_isinf)},
     {"islocked",	1, 1, FEARG_1,	    NULL,
 			ret_number_bool,    f_islocked},
-    {"isnan",		1, 1, FEARG_1,	    NULL,
+    {"isnan",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_number_bool,    MATH_FUNC(f_isnan)},
     {"items",		1, 1, FEARG_1,	    NULL,
 			ret_list_any,	    f_items},
@@ -1160,13 +1164,13 @@
 			ret_number,	    f_listener_add},
     {"listener_flush",	0, 1, FEARG_1,	    NULL,
 			ret_void,	    f_listener_flush},
-    {"listener_remove",	1, 1, FEARG_1,	    NULL,
+    {"listener_remove",	1, 1, FEARG_1,	    arg1_number,
 			ret_number_bool,    f_listener_remove},
     {"localtime",	0, 0, 0,	    NULL,
 			ret_number,	    f_localtime},
-    {"log",		1, 1, FEARG_1,	    NULL,
+    {"log",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_log)},
-    {"log10",		1, 1, FEARG_1,	    NULL,
+    {"log10",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_log10)},
     {"luaeval",		1, 2, FEARG_1,	    NULL,
 			ret_any,
@@ -1192,9 +1196,9 @@
 			ret_number,	    f_matchadd},
     {"matchaddpos",	2, 5, FEARG_1,	    NULL,
 			ret_number,	    f_matchaddpos},
-    {"matcharg",	1, 1, FEARG_1,	    NULL,
+    {"matcharg",	1, 1, FEARG_1,	    arg1_number,
 			ret_list_string,    f_matcharg},
-    {"matchdelete",	1, 2, FEARG_1,	    NULL,
+    {"matchdelete",	1, 2, FEARG_1,	    arg2_number,
 			ret_number_bool,    f_matchdelete},
     {"matchend",	2, 4, FEARG_1,	    NULL,
 			ret_number,	    f_matchend},
@@ -1236,7 +1240,7 @@
 			ret_number,	    f_nextnonblank},
     {"nr2char",		1, 2, FEARG_1,	    NULL,
 			ret_string,	    f_nr2char},
-    {"or",		2, 2, FEARG_1,	    NULL,
+    {"or",		2, 2, FEARG_1,	    arg2_number,
 			ret_number,	    f_or},
     {"pathshorten",	1, 2, FEARG_1,	    NULL,
 			ret_string,	    f_pathshorten},
@@ -1290,7 +1294,7 @@
 			ret_void,	    PROP_FUNC(f_popup_settext)},
     {"popup_show",	1, 1, FEARG_1,	    NULL,
 			ret_void,	    PROP_FUNC(f_popup_show)},
-    {"pow",		2, 2, FEARG_1,	    NULL,
+    {"pow",		2, 2, FEARG_1,	    arg2_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_pow)},
     {"prevnonblank",	1, 1, FEARG_1,	    NULL,
 			ret_number,	    f_prevnonblank},
@@ -1398,7 +1402,7 @@
 			ret_string,	    f_resolve},
     {"reverse",		1, 1, FEARG_1,	    NULL,
 			ret_first_arg,	    f_reverse},
-    {"round",		1, 1, FEARG_1,	    NULL,
+    {"round",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_round)},
     {"rubyeval",	1, 1, FEARG_1,	    NULL,
 			ret_any,
@@ -1408,11 +1412,11 @@
 	    NULL
 #endif
 			},
-    {"screenattr",	2, 2, FEARG_1,	    NULL,
+    {"screenattr",	2, 2, FEARG_1,	    arg2_number,
 			ret_number,	    f_screenattr},
-    {"screenchar",	2, 2, FEARG_1,	    NULL,
+    {"screenchar",	2, 2, FEARG_1,	    arg2_number,
 			ret_number,	    f_screenchar},
-    {"screenchars",	2, 2, FEARG_1,	    NULL,
+    {"screenchars",	2, 2, FEARG_1,	    arg2_number,
 			ret_list_number,    f_screenchars},
     {"screencol",	0, 0, 0,	    NULL,
 			ret_number,	    f_screencol},
@@ -1420,7 +1424,7 @@
 			ret_dict_number,    f_screenpos},
     {"screenrow",	0, 0, 0,	    NULL,
 			ret_number,	    f_screenrow},
-    {"screenstring",	2, 2, FEARG_1,	    NULL,
+    {"screenstring",	2, 2, FEARG_1,	    arg2_number,
 			ret_string,	    f_screenstring},
     {"search",		1, 5, FEARG_1,	    NULL,
 			ret_number,	    f_search},
@@ -1448,7 +1452,7 @@
 			ret_number_bool,    f_setcharpos},
     {"setcharsearch",	1, 1, FEARG_1,	    NULL,
 			ret_void,	    f_setcharsearch},
-    {"setcmdpos",	1, 1, FEARG_1,	    NULL,
+    {"setcmdpos",	1, 1, FEARG_1,	    arg1_number,
 			ret_number_bool,    f_setcmdpos},
     {"setcursorcharpos", 1, 3, FEARG_1,	    NULL,
 			ret_number_bool,    f_setcursorcharpos},
@@ -1486,7 +1490,7 @@
 			},
     {"shellescape",	1, 2, FEARG_1,	    NULL,
 			ret_string,	    f_shellescape},
-    {"shiftwidth",	0, 1, FEARG_1,	    NULL,
+    {"shiftwidth",	0, 1, FEARG_1,	    arg1_number,
 			ret_number,	    f_shiftwidth},
     {"sign_define",	1, 2, FEARG_1,	    NULL,
 			ret_any,	    SIGN_FUNC(f_sign_define)},
@@ -1508,9 +1512,9 @@
 			ret_list_number,    SIGN_FUNC(f_sign_unplacelist)},
     {"simplify",	1, 1, FEARG_1,	    NULL,
 			ret_string,	    f_simplify},
-    {"sin",		1, 1, FEARG_1,	    NULL,
+    {"sin",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_sin)},
-    {"sinh",		1, 1, FEARG_1,	    NULL,
+    {"sinh",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_sinh)},
     {"slice",		2, 3, FEARG_1,	    NULL,
 			ret_first_arg,	    f_slice},
@@ -1532,7 +1536,7 @@
 			ret_list_string,    f_spellsuggest},
     {"split",		1, 3, FEARG_1,	    NULL,
 			ret_list_string,    f_split},
-    {"sqrt",		1, 1, FEARG_1,	    NULL,
+    {"sqrt",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_sqrt)},
     {"srand",		0, 1, FEARG_1,	    NULL,
 			ret_list_number,    f_srand},
@@ -1616,9 +1620,9 @@
 			ret_list_string,    f_tagfiles},
     {"taglist",		1, 2, FEARG_1,	    NULL,
 			ret_list_dict_any,  f_taglist},
-    {"tan",		1, 1, FEARG_1,	    NULL,
+    {"tan",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_tan)},
-    {"tanh",		1, 1, FEARG_1,	    NULL,
+    {"tanh",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_tanh)},
     {"tempname",	0, 0, 0,	    NULL,
 			ret_string,	    f_tempname},
@@ -1750,15 +1754,15 @@
 			ret_void,	    TIMER_FUNC(f_timer_stop)},
     {"timer_stopall",	0, 0, 0,	    NULL,
 			ret_void,	    TIMER_FUNC(f_timer_stopall)},
-    {"tolower",		1, 1, FEARG_1,	    NULL,
+    {"tolower",		1, 1, FEARG_1,	    arg1_string,
 			ret_string,	    f_tolower},
-    {"toupper",		1, 1, FEARG_1,	    NULL,
+    {"toupper",		1, 1, FEARG_1,	    arg1_string,
 			ret_string,	    f_toupper},
-    {"tr",		3, 3, FEARG_1,	    NULL,
+    {"tr",		3, 3, FEARG_1,	    arg3_string,
 			ret_string,	    f_tr},
     {"trim",		1, 3, FEARG_1,	    NULL,
 			ret_string,	    f_trim},
-    {"trunc",		1, 1, FEARG_1,	    NULL,
+    {"trunc",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_float,	    FLOAT_FUNC(f_trunc)},
     {"type",		1, 1, FEARG_1,	    NULL,
 			ret_number,	    f_type},
@@ -1784,27 +1788,27 @@
 			ret_list_number,    f_win_findbuf},
     {"win_getid",	0, 2, FEARG_1,	    NULL,
 			ret_number,	    f_win_getid},
-    {"win_gettype",	0, 1, FEARG_1,	    NULL,
+    {"win_gettype",	0, 1, FEARG_1,	    arg1_number,
 			ret_string,	    f_win_gettype},
-    {"win_gotoid",	1, 1, FEARG_1,	    NULL,
+    {"win_gotoid",	1, 1, FEARG_1,	    arg1_number,
 			ret_number_bool,    f_win_gotoid},
-    {"win_id2tabwin",	1, 1, FEARG_1,	    NULL,
+    {"win_id2tabwin",	1, 1, FEARG_1,	    arg1_number,
 			ret_list_number,    f_win_id2tabwin},
-    {"win_id2win",	1, 1, FEARG_1,	    NULL,
+    {"win_id2win",	1, 1, FEARG_1,	    arg1_number,
 			ret_number,	    f_win_id2win},
-    {"win_screenpos",	1, 1, FEARG_1,	    NULL,
+    {"win_screenpos",	1, 1, FEARG_1,	    arg1_number,
 			ret_list_number,    f_win_screenpos},
     {"win_splitmove",   2, 3, FEARG_1,	    NULL,
 			ret_number_bool,    f_win_splitmove},
-    {"winbufnr",	1, 1, FEARG_1,	    NULL,
+    {"winbufnr",	1, 1, FEARG_1,	    arg1_number,
 			ret_number,	    f_winbufnr},
     {"wincol",		0, 0, 0,	    NULL,
 			ret_number,	    f_wincol},
     {"windowsversion",	0, 0, 0,	    NULL,
 			ret_string,	    f_windowsversion},
-    {"winheight",	1, 1, FEARG_1,	    NULL,
+    {"winheight",	1, 1, FEARG_1,	    arg1_number,
 			ret_number,	    f_winheight},
-    {"winlayout",	0, 1, FEARG_1,	    NULL,
+    {"winlayout",	0, 1, FEARG_1,	    arg1_number,
 			ret_list_any,	    f_winlayout},
     {"winline",		0, 0, 0,	    NULL,
 			ret_number,	    f_winline},
@@ -1816,13 +1820,13 @@
 			ret_void,	    f_winrestview},
     {"winsaveview",	0, 0, 0,	    NULL,
 			ret_dict_number,    f_winsaveview},
-    {"winwidth",	1, 1, FEARG_1,	    NULL,
+    {"winwidth",	1, 1, FEARG_1,	    arg1_number,
 			ret_number,	    f_winwidth},
     {"wordcount",	0, 0, 0,	    NULL,
 			ret_dict_number,    f_wordcount},
     {"writefile",	2, 3, FEARG_1,	    NULL,
 			ret_number_bool,    f_writefile},
-    {"xor",		2, 2, FEARG_1,	    NULL,
+    {"xor",		2, 2, FEARG_1,	    arg2_number,
 			ret_number,	    f_xor},
 };