Left side of equations, inequalities, relations, intervals, ranges and tables

Use only in the MuPAD Notebook Interface.

This functionality does not run in MATLAB.




lhs(f) returns the left side of f.

The call lhs(f) is equivalent to the direct call op(f,1), of the operand function op, if f is not a table.

If t is a table, the call lhs(t) returns the list of keys of the table (left side). Note that the ith value in rhs(t) corresponds to the ith key in lhs(t).


Example 1

Extract the left sides of various objects:

lhs(x = sin(2)), lhs(3.14 <> PI), lhs(x + 3 < 2*y)

The operands of an expression depend on its internal representation. In particular, a "greater" relation is always converted to the corresponding "less" relation:

y > -infinity;
lhs(y > -infinity)

y >= 4;
lhs(y >= 4)

Example 2

Extract the left sides of the solution of the following system:

s := solve({x + y = 1, 2*x - 3*y = 2})

map(op(s), lhs)

Calls to lhs can be easier to read than the equivalent calls to the operand function op:

map(op(s), op, 1)

However, direct calls to op must be preferred inside procedures for higher efficiency.

delete s:

Example 3

Extract the keys (left side) and values (right side) from a table:

t := table(1=2, 4=PI, 5=5.6, 19=1/2):
l := lhs(t);

r := rhs(t);

Note that the ith value corresponds to the ith key:

bool(r = map(lhs(t), e->t[e]))

delete t,l,r:



An equation x = y, an inequality x <> y, a relation x < y, a relation x <= y, an "is element of"-relation x in y, an interval x...y, a range x..y, or a table table(x=y,...).

Overloaded By


See Also

MuPAD Functions

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