ch vex function

Contexts: chop , pop , sop

Tags: utility

Evaluates a channel (or parameter) and return its value.

1. float ch(string channel)

2. string ch(string channel)

3. float ch(string channel, float time)

4. string ch(string channel, float time)

Evaluates a channel (or parameter) and return its value. When evaluating string parameters at a specified time, the time value must be the same for all evaluations of the parameter.

If the time is not constant over the all the points/pixels being evaluated, results are not predictable. For example, the following functions will produce unpredictable results:

string s = ch(channel_path, ptnum);        // SOP/POP
string s = ch(channel_path, cinput(X, Y).r);    // COP
string s = ch(channel_path, age);        // SOP/POP
string s = ch(channel_path, V);            // CHOP

string s = ch(channel_path, Time*.7);    // SOP/POP
string s = ch(channel_path, XRES);    // COP
string s = ch(channel_path, SR);    // CHOP