Q E P C A D - QEPCAD Interface Documentation

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qepcad.help

Each command has an entree in qepcad.help that looks something like:

d-all-cells-in-subtree 48 de d
@
d-all-cells-in-subtree C 

Displays the info about all the cells in the subtree
rooted at the cell with index C.
@
	

The first line contains the command's name (d-all-cells-in-subtree in this case), a unique identifying number for the command (48 in this case), a string that is a substring of "abcde" (de in this case) which defines the phases of the program in which the command is available, and a string that is one of pc, d, proj, a, m, cp (d in this case) indicating the type ofthe command. The command types are defined at the end of qepcad.help

pc @Program control:@
d @Displaying information:@
proj @Modifying the projection set:@
a @Selecting algorithms:@
m @Miscellaneous:@
cp @Chris's Play:@
	

What appears between the @'s is just documentation that's available to the QEPCAD user via the whatis command.

USERINT.c

QEPCAD gets input from the user by calling the function USERINT defined in USERINT.c. This function calls GETCID which reads in a command from the user, matches it with a command definition in qepcad.help, and returns the unique id number for that command. The remainder of USERINT is a big switch statement that switches on that id and performs the associated action.

Adding a command to QEPCAD thus consists of adding the appropriate entry to qepcad.help, and adding a line for the new index to the switch statement in USERINT.c.