predeclared-variables

general
   Constants      hoc_ac_        hoc_cross_y_   
   float_epsilon  hoc_cross_x_   hoc_obj_

float_epsilon

predeclared-variables

SYNTAX

float_epsilon = 1e-11

DESCRIPTION

The default value is 1e-11

Allows somewhat safer logical comparisons and integer truncation for floating point numbers. Most comparisons are treated as true if they are within float_epsilon of being true. eg.

execute following example 

for (i = 0; i < 1; i += .1) {
	print i, int(10*i)
}
float_epsilon = 0
// two bugs due to roundoff
for (i = 0; i < 1; i += .1) {
	print i, int(10*i)
}

BUGS

I certainly haven't gotten every floating comparison in the program to use float_epsilon but I have most of them including all interpreter logical operations, int, array indices, and Vector logic methods.

hoc_ac_

predeclared-variables
A variable used by the graphical interface to communicate with the interpreter. It is very volatile. It sometimes holds a value on a function call. If this value is needed by the user it should be copied to another variable prior to any other function call.

hoc_obj_

predeclared-variables

SYNTAX

hoc_obj_[0]
hoc_obj_[1]

DESCRIPTION

When a line on a Graph is picked with the PickVector tool two new Vector 's are created containing the y and x coordinates of the line. The y vector is referenced by hoc_obj_[0] and the x vector is referenced by hoc_obj_[1].

hoc_cross_x_

predeclared-variables

SYNTAX

hoc_cross_x_

DESCRIPTION

X coordinate value of the last Crosshair manipulation.

SEE ALSO

crosshair

hoc_cross_y_

predeclared-variables

DESCRIPTION

Y coordinate value of the last Crosshair manipulation.

SEE ALSO

crosshair

Constants

predeclared-variables
The following mathematical and physical constants are built-in: 
        "PI",   3.14159265358979323846,
        "E",    2.71828182845904523536,
        "GAMMA",0.57721566490153286060, /* Euler */
        "DEG", 57.29577951308232087680, /* deg/radian */
        "PHI",  1.61803398874989484820, /* golden ratio */
        "FARADAY", 96484.56,    /*coulombs/mole*/
        "R", 8.31441,           /*molar gas constant, joules/mole/deg-K*/

BUGS

Constants are not treated specially by the interpreter and may be changed with assignment statements.

The FARADAY is a bit different than the faraday of the units database. The faraday in a .mod mechanism is 96520.

neuron/general/predec.hel : May 13 2012