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Diffstat (limited to 'bool.notes')
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diff --git a/bool.notes b/bool.notes new file mode 100644 index 00000000..8e24c2b5 --- /dev/null +++ b/bool.notes @@ -0,0 +1,53 @@ +Thu Mar 18 21:05:29 IST 2021 +============================ + +Design Notes for a Boolean Type in Gawk + +1. A new function bool(val) converts val to bool, returning Boolean TRUE +or FALSE. This is the generator for boolean values and is enough to have +instead of predefining new variables TRUE and FALSE. + +2. Assigning from a boolean value copies the bool type. + +3. Boolean variables have numeric values 1 and 0 respectively, and string +values "TRUE" and "FALSE". Thus they differ from other variables where a +"false" value must be zero and null. + +Given: + + true = bool(1) + false = bool(0) + +this implies all of the following: + + print(true) --> "TRUE" + print(false) --> "FALSE" + Same for %s in printf + Same for bool_var "" + printf %d gives 0/1 + +4. typeof() returns "bool". + +5. Numeric operators treat booleans as numbers. asort() sorts booleans before +numbers, and false before true. + +6. These string function generate a runtime fatal error +if given an argument / target of boolean type: + + gsub sub + +These functions merely treat the value as a string +but issue a lint warning. + + substr match index gensub + length split patsplit + tolower toupper + +7. Updates to API needed for an additional type, and the table +for requested vs. returns. + +8. The following extensions need revising: + + - JSON extension + - dump / read array extensions + - what else? |