diff --git a/c/mapping/lrec_evaluators.c b/c/mapping/lrec_evaluators.c
index 2067912ac..41c5b0f80 100644
--- a/c/mapping/lrec_evaluators.c
+++ b/c/mapping/lrec_evaluators.c
@@ -398,6 +398,32 @@ lrec_evaluator_t* lrec_evaluator_alloc_from_s_x_func(mv_unary_func_t* pfunc, lre
 	return pevaluator;
 }
 
+// ----------------------------------------------------------------
+typedef struct _lrec_evaluator_b_x_state_t {
+	mv_unary_func_t*  pfunc;
+	lrec_evaluator_t* parg1;
+} lrec_evaluator_b_x_state_t;
+
+mv_t lrec_evaluator_b_x_func(lrec_t* prec, context_t* pctx, void* pvstate) {
+	lrec_evaluator_b_x_state_t* pstate = pvstate;
+	mv_t val1 = pstate->parg1->pevaluator_func(prec, pctx, pstate->parg1->pvstate);
+	return pstate->pfunc(&val1);
+}
+
+lrec_evaluator_t* lrec_evaluator_alloc_from_b_x_func(mv_unary_func_t* pfunc,
+	lrec_evaluator_t* parg1)
+{
+	lrec_evaluator_b_x_state_t* pstate = mlr_malloc_or_die(sizeof(lrec_evaluator_b_x_state_t));
+	pstate->pfunc = pfunc;
+	pstate->parg1 = parg1;
+
+	lrec_evaluator_t* pevaluator = mlr_malloc_or_die(sizeof(lrec_evaluator_t));
+	pevaluator->pvstate = pstate;
+	pevaluator->pevaluator_func = lrec_evaluator_b_x_func;
+
+	return pevaluator;
+}
+
 // ----------------------------------------------------------------
 typedef struct _lrec_evaluator_b_xx_state_t {
 	mv_binary_func_t* pfunc;
@@ -751,6 +777,7 @@ static function_lookup_t FUNCTION_LOOKUP_TABLE[] = {
 	{ FUNC_CLASS_CONVERSION, "float",    1 , "Convert int/float/bool/string to float."},
 	{ FUNC_CLASS_CONVERSION, "int",      1 , "Convert int/float/bool/string to int."},
 	{ FUNC_CLASS_CONVERSION, "string",   1 , "Convert int/float/bool/string to string."},
+	{ FUNC_CLASS_CONVERSION, "boolean",  1 , "Convert int/float/bool/string to boolean."},
 
 	{ FUNC_CLASS_TIME, "gmt2sec",  1 , "Parses GMT timestamp as integer seconds since epoch."},
 	{ FUNC_CLASS_TIME, "sec2gmt",  1 , "Formats seconds since epoch (integer part only) as GMT timestamp."},
@@ -883,6 +910,7 @@ lrec_evaluator_t* lrec_evaluator_alloc_from_unary_func_name(char* fnnm, lrec_eva
 	} else if (streq(fnnm, "asinh"))    { return lrec_evaluator_alloc_from_f_f_func(f_f_asinh_func,    parg1);
 	} else if (streq(fnnm, "atan"))     { return lrec_evaluator_alloc_from_f_f_func(f_f_atan_func,     parg1);
 	} else if (streq(fnnm, "atanh"))    { return lrec_evaluator_alloc_from_f_f_func(f_f_atanh_func,    parg1);
+	} else if (streq(fnnm, "boolean"))  { return lrec_evaluator_alloc_from_b_x_func(b_x_boolean_func,  parg1);
 	} else if (streq(fnnm, "cbrt"))     { return lrec_evaluator_alloc_from_f_f_func(f_f_cbrt_func,     parg1);
 	} else if (streq(fnnm, "ceil"))     { return lrec_evaluator_alloc_from_f_f_func(f_f_ceil_func,     parg1);
 	} else if (streq(fnnm, "cos"))      { return lrec_evaluator_alloc_from_f_f_func(f_f_cos_func,      parg1);
diff --git a/c/mapping/mlr_val.c b/c/mapping/mlr_val.c
index 9254f75ea..812135743 100644
--- a/c/mapping/mlr_val.c
+++ b/c/mapping/mlr_val.c
@@ -312,6 +312,28 @@ static mv_unary_func_t* float_dispositions[MT_MAX] = {
 
 mv_t f_x_float_func(mv_t* pval1) { return (float_dispositions[pval1->type])(pval1); }
 
+// ----------------------------------------------------------------
+static mv_t boolean_b_n(mv_t* pa) { return (mv_t) {.type = MT_NULL,  .u.intv = 0}; }
+static mv_t boolean_b_e(mv_t* pa) { return (mv_t) {.type = MT_ERROR, .u.intv = 0}; }
+static mv_t boolean_b_b(mv_t* pa) { return (mv_t) {.type = MT_BOOL,  .u.boolv = pa->u.boolv}; }
+static mv_t boolean_b_d(mv_t* pa) { return (mv_t) {.type = MT_BOOL,  .u.boolv = (pa->u.dblv == 0.0) ? FALSE : TRUE}; }
+static mv_t boolean_b_i(mv_t* pa) { return (mv_t) {.type = MT_BOOL,  .u.boolv = (pa->u.intv == 0LL) ? FALSE : TRUE}; }
+static mv_t boolean_b_s(mv_t* pa) { return (mv_t) {.type = MT_BOOL,
+		.u.boolv = (streq(pa->u.strv, "true") || streq(pa->u.strv, "TRUE")) ? TRUE : FALSE
+	};
+}
+
+static mv_unary_func_t* boolean_dispositions[MT_MAX] = {
+    /*NULL*/   boolean_b_n,
+    /*ERROR*/  boolean_b_e,
+    /*BOOL*/   boolean_b_b,
+    /*DOUBLE*/ boolean_b_d,
+    /*INT*/    boolean_b_i,
+    /*STRING*/ boolean_b_s,
+};
+
+mv_t b_x_boolean_func(mv_t* pval1) { return (boolean_dispositions[pval1->type])(pval1); }
+
 // ----------------------------------------------------------------
 static mv_t string_s_n(mv_t* pa) { return (mv_t) {.type = MT_NULL,   .u.intv = 0}; }
 static mv_t string_s_e(mv_t* pa) { return (mv_t) {.type = MT_ERROR,  .u.intv = 0}; }
diff --git a/c/mapping/mlr_val.h b/c/mapping/mlr_val.h
index eb392e87a..3aaaa6a3c 100644
--- a/c/mapping/mlr_val.h
+++ b/c/mapping/mlr_val.h
@@ -127,6 +127,7 @@ static inline mv_t f_f_uneg_func(mv_t*     pval1){mv_t rv={.type=MT_DOUBLE,.u.db
 
 mv_t i_x_int_func(mv_t* pval1);
 mv_t f_x_float_func(mv_t* pval1);
+mv_t b_x_boolean_func(mv_t* pval1);
 mv_t s_x_string_func(mv_t* pval1);
 
 // ----------------------------------------------------------------
diff --git a/c/todo.txt b/c/todo.txt
index 30234338a..9e58195ac 100644
--- a/c/todo.txt
+++ b/c/todo.txt
@@ -10,6 +10,7 @@ TOP OF LIST
 !! booleans into put-dsl: should be able to do: mlr put '$ok = $x < 10'
   -> boolean literal parsing? on by default? doc why not if not. (various words in text columns,
      some ('true','false') suddenly changing type -- ick.)
+  -> boolean() function then??
   -> certainly, for output: want mlr put '$z=true'
   -> UTs