GRASS (programming language): Difference between revisions

Revision as of 17:08, 13 March 2023

Revision as of 17:08, 13 March 2023

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Programs in Zgrass were referred to as "macros", and stored as strings. Both of these oddities were deliberate, as Zgrass allowed any string to become a program. For instance, <code>MYBOX="BOX 0,0,100,100,2"</code> defines a string (no need for a $ on the variable as in [[Microsoft BASIC]]s) containing a snippet of Zgrass code. Simply typing {{code|MYBOX}} from that point on would run the command(s) inside. This feature can be used in place of the more traditional <code>GOSUB</code> command from BASIC, but has the added advantage of having a well-defined name as opposed to an opaque line number. In addition, the command remains in the form of a string in memory and can be manipulated at runtime with standard string operations.

Most BASIC [[interpreter (computer softwarecomputing)|interpreters]] of the era converted the input text into a ''[[Lexical analysis|tokenized]]'' version in which each of the commands was replaced by a single number (typically one [[byte]] long). This made the program run faster because it didn't have to continually decode the commands from the strings every time. Zgrass's use of string-based macros made this difficult, so they didn't bother with tokenization. Instead, they included a [[compiler]] which could be used on any particular macro, speeding it up many times. Programs would often consist of a mix of compiled and uncompiled macros.

Line numbers were optional in Zgrass, and typically only appeared on lines that were the target of a <code>GOTO</code>. Most BASIC interpreters required line numbers for every line of code, but this was due to their use in the "line editor"&ndash;if you needed to edit a particular line, the only way to refer to it was by number. Zgrass used a more advanced full-screen editor that eliminated this need. Zgrass allowed any string to act as a "line number", {{code|GOTO 10}} and {{code|GOTO MARKER}} were both valid.