Literal prettyprinting protocol
Factor handbook » Developer tools » The prettyprinter » Extending the prettyprinter
Factor handbook » Developer tools » The prettyprinter » Extending the prettyprinter
| Next: | Prettyprinting more complex literals |
Most custom data types have a literal syntax which resembles a sequence. An easy way to define such a syntax is to add a method to the pprint* generic word which calls pprint-object, and then to provide methods on two other generic words:
For example, consider the following data type, together with a parsing word for creating literals:
An example literal might be:
Without further effort, the literal does not print in the same way:
However, we can define three methods easily enough:
Now, it will be printed in a custom way:
pprint-delims ( obj -- start end )
>pprint-sequence ( obj -- seq )
For example, consider the following data type, together with a parsing word for creating literals:
TUPLE: rect w h ;
SYNTAX: RECT[
scan-number
scan-token "*" assert=
scan-number
scan-token "]" assert=
<rect> suffix! ;
An example literal might be:
RECT[ 100 * 200 ]
Without further effort, the literal does not print in the same way:
RECT[ 100 * 200 ] .
T{ rect f 100 200 }
T{ rect f 100 200 }
However, we can define three methods easily enough:
M: rect pprint-delims drop \ RECT[ \ ] ;
M: rect >pprint-sequence dup w>> \ * rot h>> 3array ;
M: rect pprint* pprint-object ;
Now, it will be printed in a custom way:
RECT[ 100 * 200 ] .
RECT[ 100 * 200 ]
RECT[ 100 * 200 ]