Introduce 'function' built-in. #77
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Perhaps some documentation and tests? |
Krush206
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Krush206
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Nov 22, 2023
As requested in tcsh-org#4, here's my proposal. This is a wrapper around goto and source. The script recurses itself and searches for a goto label. It's an error for labels not contain an exit to their end. Function calls outside labels are, by default, labeled main. This was tested sparsely, and may contain bugs I haven't faced, but is working as expected. One bug to be noted is that pipes don't give up on errors. This is possibly due to forking. I noticed Tcsh has a built-in function command, but I can't trace the code. Said built-in function command is evaluated before mine, thus those who attempt to execute it won't get the correct error message.
Next, make a table of functions so they can be called globally. Currently, it isn't possible to call functions from sourced files other than the current.
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I think functions based on pipes makes a simpler feature, as well as allows for use in interactive sessions, resembling Bourne-compatible Shells better. Unlike the goto-based version, this new version only allows functions be called if they were previously declared (i.e: no forward jumps), making a similar behavior to Bourne-compatible Shells. This version relies on a tree derived from variables and aliases. Unlike to aliases and variables, the tree is restrictive. Once a function is declared, may not be redeclared or undeclared. |
I think functions based on pipes makes a simpler feature, as well as allows for use in interactive sessions, resembling Bourne-compatible Shells better. Unlike the goto-based version, functions may only be called if they were previously declared (i.e: no forward jumps), making a similar behavior to Bourne-compatible Shells. This version relies on a tree derived from variables and aliases. Unlike to aliases and variables, the tree is restrictive. Once a function is declared, may not be redeclared or undeclared. I was afraid this wouldn't work out for some operations, such as loops and gotos, because pipes cannot rewind. Fortunately, I was wrong, and the fact these operations are possible from interactive sessions, from a terminal, makes the assumption just as wrong, though I'm clueless as to how rewinding is possible on unsupported sources.
Though POSIX defines a minimum for pipe buffer, I decided is safer writing one byte a time. This may render slow reads, though writing in larger quantities rendered broken reads. For an unknown reason, some operations, after SIGINT, rendered exiting the Shell. This happens on the ERR_RECURSION error as well. longjmp remedies the issue, though I'm afraid isn't the best solution.
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As requested in #4, here's my proposal. This is a wrapper around
gotoandsource. The script recurses itself and searches for agotolabel. It's an error for labels not contain anexitto their end. Function calls outside labels are, by default, labeledmain.This was tested sparsely, and may contain bugs I haven't faced, but is working as expected. One bug to be noted is that pipes don't give up on errors. This is possibly due to forking.
I noticed Tcsh has a built-in
functioncommand, but I can't trace the code. Said built-infunctioncommand is evaluated before mine, thus those who attempt to execute it won't get the correct error message.