Your mentioning "ALTER" made me think about a dialect of BASIC that I once used (STARDOS BASIC on a "Micro V" computer, back in the late 1980s). This BASIC dialect had an "XEQ" function that would pass a string to the tokenizer and execute it as an immediate-mode command. If you started the string with a line number you could create self-modifying BASIC code. It was dizzying to my young mind.
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Your mentioning "ALTER" made me think about a dialect of BASIC that I once used (STARDOS BASIC on a "Micro V" computer, back in the late 1980s). This BASIC dialect had an "XEQ" function that would pass a string to the tokenizer and execute it as an immediate-mode command. If you started the string with a line number you could create self-modifying BASIC code. It was dizzying to my young mind.